Turbochargers, and superchargers, may be used with internal combustion engines to increase the mass of air entering the combustion chamber of the engine to create more power. An inlet compressor in the form of, for example, a radial fan pump may be disposed in an inlet duct to compress inlet air. In some cases the inlet compressor may be driven by the energy of the exhaust gases of the engine.
Airflow characteristics at an inlet compressor inlet may affect turbo inlet efficiency and reduce turbulence related noise by providing additional margin to the compressor surge line. Specifically, the direction of swirl relative to the compressor rotation direction can affect both efficiency and noise. If the swirl direction is opposite from the compressor, turbulence and noise can result, sometimes referred to as tip-in whoosh. Inducing a swirl in the same direction as the compressor can result in improved inlet efficiency (higher mass flow rate) and reduced noise generation.
U.S. Pat. No. 7,322,191 discloses a device for imparting a whirling motion on the flow of air for supplying a turbo-supercharged internal-combustion engine. The device is designed to be interposed upstream from the elbow of an elbow-shaped duct. The duct supplies air to the supercharger. The duct has an upstream branch having a square, or rectangular, cross-section, and a downstream branch having a circular section to facilitate formation of a helical flow through the downstream branch. A vane is mounted oscillating about an axis in the upstream branch. In this way, the downstream branch of the elbow portion is reached by a tangential flow that gives rise to the helical flow of the air in the downstream branch. A maximum effect in the generation of the whirling movement is obtained when the vane is at maximum inclination.
The inventors herein have recognized issues relating to this approach. As one example, the approach causes the greatest resistance to flow through the duct to achieve maximum effect in the generation of the whirling movement.
To address the above issues, a duct with highly engineered geometry, potentially via computational fluid dynamics (CFD) or physical test methods, for directing an inlet flow into an inlet compressor of an internal combustion engine may be provided. The inlet duct may include one or more relief features disposed on an inner surface of the inlet duct. The one or more relief features may be disposed to protrude into the inlet flow to cause the inlet flow to swirl before reaching the inlet compressor. In one example, the one or more relief features may be made integral with the inlet duct. Various example embodiments may provide the required swirl ratios with minimal added restriction, cost, manufacturing, and assembly limitations.
Various embodiments may provide elements such as relief features, internal vanes, and/or rifling to compressor inlet ducts to rotate, or swirl an inlet flow before impacting a compressor. The relief features may be formed on an inside surface of the inlet duct by forming troughs in the outside surface. The elements may tune both the direction and magnitude of rotation. The one or more of vanes, rifling, or troughs may be added to the induction system via a variety of methods including, but not limited to, blow molded, injection molded, cast, or hydro-formed metal ducts. In one example, the rifling protrusions from the exterior of the inlet ducts form a screw-shaped pattern to impart rotational flow about the central axis of the duct, the screw-shaped pattern rotating along the length of the duct toward the turbocharger with a rotational direction that is the same as the rotational direction of the compressor.
Various embodiments may be “tuned” during the development process. In this way, an optimal swirl ratio with minimal pressure drop may be achieved.
Various examples may be applied to turbocharged, and/or supercharged, engines for the purposes of inlet efficiency and noise control. Embodiments may be used in various applications including, without limitation, automotive applications, military applications, marine applications, aeronautic applications, and off-road usage.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.